Self-adaptive timing system for a traffic controller



Dec. 3, 1968 v CRESS, JR ET AL 3,414,877

SELF-ADAPTIVE TIMING SYSTEM FOR TRAFFIC CONTROLLER Filed Sept. 7, 1965 2 Sheets-Sheet 1 ATTDRMY Y United States Patent 0 3,414,877 SELF-ADAPTIVE TIMING SYSTEM FOR A TRAFFIC CONTROLLER Vernor B. Cress, Jr., Rowland Heights, and Philiip G.

Halamandaris, Fullerton, Calif., assignors to Tamar Electronics Industries, Inc., Los Angeles, Calif., a cor-- poration of Delaware Filed Sept. 7, 1965, Ser. No. 485,201 9 Claims. (Cl. 340-37) ABSTRACT OF THE DISCLOSURE The number of vehicles arriving at an intersection during the red and yellow timing cycles of the traflic signal is detected by means of a vehicle detector and a signal in accordance therewith registered in a counter and variable timer. The output of the variable timer is coupled to a pre-set timer for the green timing cycle of the signal and inhibits the operation thereof until the variable timer has completed its timing cycle which is in accordance with the number of vehicles which have arrived. In this manner, the green timing cycle is extended for a period of time which is in accordance with the number of vehicles held waiting during the previous red and yellow timing cycles.

This invention relates to a self-adaptive timing system for a traflic controller, and more particularly, such a system in which the green trafiic timing interval is varied in accordance with the number of vehicles held waiting durin a preceding red timing interval.

In typical traflic control systems of the prior art, the minimum green signal timing interval is determined by a pre-set timer. The timing interval so set is generally referred to as an initial" green period. Provisions are made in what is known as actuated operation to extend the green timing beyond this initial green interval in response to vehicles which may arrive on the scene during the initial green timing. No provisions are made, however, to extend the green timing in accordance with the number of vehicles waitin at the intersection when the initial green timing interval commences. Thus, unless a very long initial green timing interval is allowed under all conditions, some of the waiting vehicles may not be allowed sufiicient time to pass through the intersection. In order to optimize the efliciency of traffic control, the green timing interval should be such as to properly allow all waiting vehicles to pass, yet should not be so long as to unnecessarily tie up traflic on the cross street. The system of this invention operates to achieve these desired end results by automatically adding to the initial green signal timing interval, a timing interval which is a function of the number of vehicles which have arrived during the preceding red and yellow timing intervals. The system of this invention is such that it can readily be combined with an existing traffic controller, such as that described, for example, in co-pending application Ser. No. 467.397, filed June 28, 1965, and assigned to Tamar Eletcronics Industries, Inc., the 'assignee of the instant application.

The system of this invention achieves the desired end results in the following manner:

The output of a conventional vehicle detector which produces an output signal each time a vehicle arrives near the intersection is appropriately counted and given a desired weighting function by means of a scaling counter. This signal is registered in a counter and is subsequently utilized to control a variable timer, such that the variable timer will produce an output control signal at a time after the initiating of the green timing interval which is 3,414,877 Patented. Dec. 3, 1968 ice a function of the number of vehicles detected. The output of the variable timer is utilized in conjunction with the output of a pre-set timer in which a fixed timing is set to control the initial green timing interval. In effect, a. minimum timing interval is established by the output of the pre-set timer and time is added to this minimum green timing interval in accordance with the output of the variable timer, which changes in accordance with the waiting traffic. This end result is accomplished by delaying the commencement of the timing operation of the pre-set timer until the timing operation of the variable timer has been completed. The initial green signal timing interval thus is automatically adapted to suit changing traflic conditions.

The device of this invention utilizes digital techniques which lend themselves to solid state circuitry. This makes for compact packaging and high accuracy and reliability.

It is therefore an object of this invention to automatically adapt the green timing interval of a trafiic control system to changing traffic conditions.

It is a further object of this invention to provide a selfadaptive timing system which can readily be incorporated into an existing traific controller.

It is another object of this invention to automatically optimize the timing operation of a trafiic controller.

It is still a further object of this invention to provide a digitally implemented system for self-adapting the timing of a traffic controller.

Other objects of this invention will become apparent from the following description taken in connection with the accompanying drawings, of which:

FIG. 1 is a block diagram illustrating the basic operation of the system of this invention, and

FIG. 2 is a functional schematic diagram illustrating a preferred embodiment of the device of the invention.

Referring now to FIG. 1, a block diagram illustrating the basic operation of the device of the invention is shown.

Vehicle detector 11, which may include a conventional mechanical actuator switch, produces an output pulse 12 for each vehicle that arrives at the intersection and is held waiting by the red signal. The actuator portion of vehicle detector 11 is preferably placed back several hundred feet from the intersection so that all vehicles which may under any circumstances be held by the red trafi'ic signal are detected. Pulses 12 are passed through gate 34 when this gate is gated on by an enabling signal fed thereto from inverter 36. Inverter 36 which may, for example, comprise an inverting amplifier operates in response to green signal control 20 and produces such an enabling signal whenever green signal 19 is not being actuated by green signal control 20. The pulses are counted in scaling counter 14 which, as to be described in connection with FIG. 2, has a selector switch which enables the selective scaling or Weighting of the input pulses received to produce a selectively weighted timing signal which is a function of the number of pulses received. The output of scaling counter 14 is utilized to control counter and variable timer 16.

Green signal 19 is controlled by green signal control 20 which connects power thereto from power source 21 in response to the output of pre-set timer 25. The green timing interval is initiated by the output of pre-set timer 25, which produces a signal which actuates signal control 20. The operation of pre-set timer 25 is initiated by means of control signals generated in a traflic controller such as described in the aforementioned patent application Ser. No. 467,397. With the actuation of green signal control 20, an enabling signal is fed therefrom to counter and variable timer 16 which initiates the variable timing. When variable timer 16 is actuated, an inhibit signal is fed therefrom to pre-set timer to stop the timing operation of the timer thereof. The variable timer by virtue of its inhibit output delays the commencement of the pre-set timing interval for the timing period of the variable timing interval which is determined by the number of cars waiting to pass.

With the termination of the variable timing interval, the inhibit signal to preset timer 25 disappears and the fixed timing interval determined by the output of pre-set timer 25 commences. At the end of the fixed timing interval the green signal may be held on for an additional interval determined by traffic conditions, or the green signal may be turned off. Thus, a minimum green timing interval as set by means of pre-set timer 25 is always assured with this minimum timing interval being extended in accordance with the output of counter and variable timer 16, which is a function of the number of cars waiting to pass. The timing action of variable timer 16 is initiated by the output of signal control 20 with the initial actuation of green signal 19, variable timer 16 then producing an inhibit signal to the pre-set timer in accordance with the number of pulses previously received during the red and yellow timing intervals from scaling counter 14.

Referring now to FIG. 2, a preferred embodiment of the system of the invention is illustrated in schematic form. Vehicle detector 11, which may comprise an actuator switch located in the roadway, produces a pair of output pulses for each vehicle that passes over it. These pulses are appropriately divided down and shaped in pulse shaper and divider 32 to produce a single actuation pulse 12 for each vehicle. Pulses 12 are fed to gate 34 which also receives the output of inverter 36 as an enabling signal. Gate 34 will thus pass pulses 12 only when the green signal control 20 is not causing green signal 19 to be actuated, i.e., when the red or yellow signals are being actuated; inverter 36 having an enabling signal output to get 34 only under such conditions.

With each actuation of vehicle detector 11 by an arriving vehicle, during the time when the green signal control 20 is not holding green signal 19 on, a pulse 12 is simultaneously fed to scaling counter 40 and to flip-flop 42. Pulse 12 acts to re-set scaling counter 40, i.e., to bring it to the zero condition. Scaling counter 40 may be a conventional ring counter utilizing flip-flops.

Pulse 12 is fed from gate 34 to flip-flop 42 where it drives stage #1 to the ON condition. The output of stage #1 of flip-flop 42 is fed to gate 43 as an enabling signal. Fed to gate 43 as an input therefor is the pulse output 47 of HF. pulse signal source 50. Pulses 47 may have a frequency of the order of 5 kilocycles. The pulse output 47 of gate 43 is fed as an input to scaling counter 40. Thus, whenever flip-flop 42 is actuated by a pulse 12 indicative of the arrival of a vehicle at the intersection at any time when green signal 19 is not being held on by green signal control 20, scaling counter 40 receives input pulses 47 and counts these pulses.

Scaling switch 50 is selectively set to one of the output terminals 53 of scaling counter 40. When the counter reaches the count represented by the output stage to which switch 50 "s connected, a reset signal is fed through this switch to the #2 stage of flip-flop 42, activating this stage and thus deactivating the #1 stage, With the deactivation of the #1 stage of flip-flop 32, the enabling signal to gate 43 disappears, and this gate no longer passes pulses 47. Thus, the pulse input to scaling counter 40 is removed and counting terminated.

The setting made with switch 50' thus determines the number of pulses 47 passed through gate 43 for each actuation of vehicle detector 11. With the next actuation of vehicle detector 11 by a subsequent vehicle, scaling counter 40 is reset to the zero condition by a pulse 12 on the counters, reset line, and a subsequent count commences to permit the same number of pulses 47 to pass through gate 43. Thus, scaling counter 40 operating in conjunction with selector switch 50 provides a weighting function,

whereby the number of pulses for each actuation of vehicle detector 11 can be selected. Terminal positions 53 can be calibrated in terms of added initial green timing per car. Thus, for example, each successive terminal setting can be made to add an additional .2 second timing for each car waiting with the 10 position providing a full 2 seconds and the 1 position providing .2 second.

Counter and variable timer 16 comprises clock pulse source 62, gate 63, bidirectional counter 55 and AND gate which operate in the following manner: Pulses 47 are fed from gate 43 to bidirectional counter 55 which may be a conventional binary flip-flop counter capable of bidirectional operation. Pulses 47 drive bidirectional counter upward and are registered in this counter during the time that vehicles are accumulating when green signal 19 is not being actuated. The output 61 of clock pulse source 62 is fed to gate 63. Gate 63 is controlled by an enabling signal fed thereto from green signal control 20 when this control is holding green signal 19 on. Thus, clock pulse signals 61 are fed through gate 63 to the down input of bidirectional counter 55 only when green signal control 20 is operating so as to connect power from power source 21 to actuate green signal 19. Clock pulses 61 are preferably of a relatively low frequency which may be of the order of 5 cycles per second. For a five cycle per second clock frequency, each pulse fed to the bidirectional counter from gate 43 is weighted to .2 second, i.e., if the scaling counter is set to 5 each vehicle actuation of detector 11 causes 5 pulses to be fed to the up input of bidirectional counter 55 and counting down to zero with the clock pulses will take 1 second, thus adding this time to the initial green timing.

With the actuation of green signal 19, pulses 61 commence to drive bidirectional counter 55 downwardly, i.e., towards zero. Pulses 61 are relatively accurate in their timing, and thuse the number of pulses which are required to bring the bidirectional counter to the zero state is an accurate function of time. The number of pulses 61 required to bring bidirectional counter 55 to the Zero state depends upon the number of times vehicle detector 11 has been actuated during the red and yellow signal intervals, and therefore the time of countdown to zero is a direct function of the number of vehicles kept waiting at the trafiic signal.

Outputs from each of the stages of bidirectional counter 55 and from inverter 36 are fed to AND gate 65. When one or more of these output stages is not in the zero state or when green signal 19 is not being held on by green signal control 20, AND gate has a False output which provides an inhibit signal to pre-set timer 25. When such a False output, which may be a voltage of a predetermined magnitude, is present, it thuse inhibits or holds off the timing operation of the timer of pre-set timer 25.

When actuated by an appropriate signal generated in the traflic controller circuits (not shown), green signal control 20 connects power from power source 21 to green Signal 19. Green signal control when actuated also, as already noted, provides an enable signal to gate 63 and thus passes pulses 61 to bidirectional counter 55 to start the count down operation thereof. When bidirectional counter 55 has been driven down to the zero condition, which occurs in a time period which is a function of the number of actuations of vehicle detector 11 during the red and yellow signal conditions, AND gate 65 goes from the False to the True state. When this occurs, the inhibit signal is removed from pre-set timer 25 and the timer commences its normal initial green timing cycle. Pre-set timer 25 thus takes over the timing operation at the completion of the timing operation of bidirectional counter 55. When pre-set timer 25 has completed its timing operation, green signal control 20 may be kept actuated for an additional timing interval by virtue of vehicle actuations on the green street or the green timing may be terminated by virtue of the gating signal fed from timing control 25 to signal control 20. Such additional timing operation as well as the pre-set timer and green signal control are part of a traffic controller such as described in the aforementioned patent application Ser. No. 467,397.

When the number of vehicles waiting reaches a predetermined maximum, so as to cause bidirectional counter 55 to be filled to capacity, an inhibit signal is fed from this counter to gate 43. This inhibi signal prevents further feeding of pulses 47 to counter 55.

Gates 34, 43 and 63 may he conventional electronic gates utilizing either diode or transistorized circuitry, which is well known to those skilled in the art. OR gate 72 and AND gate 65 similarly may consist of semi-conductor circuits of conventional design.

Thus, the device of the invention provides digital means for adding timing intervals, which are a function of the number of cars accumulated at a preceding red signal, to the initial green timing set on a pre-set timer. In this manner, the trafiic control is automatically adapted to the immediate traflic conditions as they arise, with each timing cycle being optimized for such immediate conditions. This end result is achieved in a system which is suitable for ready incorporation into an existing trafiic controller, with a minimal amount of modification to existing circuitry.

While the system of this invention has been described and illustrated in detail, it is to be clearly understood that this is intended by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the following claims.

We claim: 1. In combination, a traffic controller for controlling traffic on a street, said controller including a green signal :facing said traffic, means for controlling said green signal and pre-set timer means for providing a pre-set timing signal for actuating said controlling means during a predetermined timing cycle; and a system for self-adapting the timing cycle of said green signal in accordance with the number of vehicles arriving on said street at said green signal during previous red and yellow timing cycles when said signal is not being actuated, said system comprising:

detector means for generating an output signal in accordance with the number of vehicles arriving during said previous red and yellow timing cycles,

counter and variable timer means for generating and registering a signal in accordance with the output of said detector means, and means for coupling the output of said counter and variable timer means to said pre-set timer means to inhibit the operation thereof during the timing operation of said counter and variable timer means,

whereby said green signal is actuated for a time interval which includes the predetermined timing cycle set on said pre-set timer means plus the timing output of said counter and variable timer means which varies as a function of the number of vehicles which actuate said detector means.

2. The combination as recited in claim 1 and further including scaling counter means interposed between said detector means and said counter and variable timer means for selectively weighting the output of said detector means.

3. The combination as recited in claim 2 wherein said counter and variable timer means comprises a bidirectional counter, the output of said scaling counter means being fed to drive said bidirectional counter to count upwardly, a clock pulse source, and control gate means for coupling the pulse output of said clock pulse source to drive said bidirectional counter downwardly when said green signal is actuated, said control gate means being connected to said means for controlling said green signal and being actuated in response therein.

4. A system for self-adapting the green timing cycle of a traffic controller in accordance with the number of vehicles arriving at an intersection during previous red and yellow timing cycles comprising:

detector means for producing output pulses in accordance with the number of vehicles arriving during said red and yellow timing cycles,

counter and variable timer means responsive to the output of said detector means for generating and registering a signal in accordance with said number of vehicles,

pre-set timer means for generating a predetermined timing signal,

a green signal,

signal control means for controlling said green signal,

means for coupling the output of said pre-set timer means to said signal control means to control the operation of said green signal, and

means for coupling the output of said counter and variable timer means being fed to said pre-set timer means to inhibit the operation thereof during the timing operation of said counter and variable timer means,

whereby said green signal is actuated for a time interval which includes the predetermined timing cycle set on said pre-set timer means plus the timing output of said counter and variable timer means which varies as a function of the number of vehicles which actuate said vehicle detector means.

5. The system as recited in claim 4 wherein said counter and variable timer means includes a bidirectional counter, said counter being driven upwardly in accordance with the output of said detector means, a clock pulse source, and gating means for connecting the pulse output of said clock pulse source to drive said bidirectional counter downwardly when said green signal is actuated, the timing operation of said variable timer means being completed when said bidirectional counter has been driven to zero.

6. A system for self-adapting the green timing cycle of a traffic controller in accordance with the number of vehicles arriving at an intersection during previous red and yellow timing cycles comprising:

detector means for producing output pulses in accordance with the number of vehicles arriving during said red and yellow timing cycles,

scaling counter means responsively connected to re ceive the output of said detector means for generating a preselected number of output pulses for each input pulse received from said detector means,

counter and variable timer means responsive to the output of said scaling counter means for generating a timing signal in accordance with said scaling counter means output,

pre-set timer means for generating a predetermined timing signal, a green signal, and signal control means for controlling said green signal, the output of said pre-set timer means being fed to said signal control means to control the operation thereof, the output of said counter and variable timer means being fed to said pre-set timer means to inhibit the operation thereof during the timing operation of said counter and variable timer means,

whereby said green signal is actuated for a time interval which includes the predetermined timing cycle set on said pre-set timer means plus the timing output of said counter and variable timer means which varies as a function of the number of vehicles which actuate said detector means.

7. The system as recited in claim 6 wherein said scaling counter means comprises a ring counter having a plurality of stages, a high frequency pulse source, gating means for feeding pulses from said high frequency pulse source to the input of said ring counter in response to the output pulses of said detector means, and selector switch means for selectively connecting the output of one of said counter stages to said gating means to stop the feeding of pulses therethrough when said one of said counter stages is actuated.

8. The system as recited in claim 6 wherein said counter and variable timer means includes a bidirectional counter, the pulse count of said scaling counter being fed to said variable timer to drive said bidirectional counter upwardly, a clock pulse source, and gating means for connecting the pulse output of said clock pulse source to drive said bidirectional counter downwardly when said green signal is actuated, the timing output of said counter and variable timer means being the time it takes for said bidirectional timer to count down to zero.

9. A system for self-adapting the green timing cycle of a traflic controller in accordance with the number of vehicles arriving at an intersection during previous red and yellow timing intervals comprising:

means for generating a pre-selected number of output pulses for each vehicle arriving at said intersection during said previous red and yellow timing intervals,

counter and variable timer means responsive to said pulse generating means for generating and registering a signal in accordance with the number of pulses generated by said pulse generating means,

pre-set timer means for generating a predetermined timing signal,

a green signal,

signal control means for controlling said green signal,

means for coupling the output of said pre-set timer means to said signal control means to control the operation of said green signal, and

means for coupling the output of said counter and variable timer means to said pre-set timer means to inhibit the operation thereof during the timing operation of said counter and variable timer means,

whereby said green signal is actuated for a time interval which includes the pre-determined timing cycle set on said pre-set timer means plus the timing output of said counter and variable timer means which varies as a function of the number of vehicles arriving at said intersection during previous red and yellow timing intervals.

References Cited UNITED STATES PATENTS 2,135,472 11/1938 Renshaw 340-37 2,506,368 5/1950 Leonard 34O-37 25 THOMAS B. HABECKER, Primary Examiner. 

